Stenosemus vendrascoi, Dell’Angelo & Sosso & Taviani, 2025

Stenosemus vendrascoi sp. nov.

Fig. 80 View FIGURE 80

Stenosemus sp. A View in CoL Dell’Angelo, Giuntelli, Sosso & Zunino, 2015a, p. 235, pl. 6, figs 10–11.

Type material. Holotype: MSNG 62658 View Materials , tail valve, width 4 mm ( Figs 80A–D View FIGURE 80 ) . Paratype 1: MSNG 62659 View Materials , intermediate valve, width 3.2 mm ( Figs 80E–F View FIGURE 80 ) . Paratype 2: MSNG 62660 View Materials , head valve, width 4.3 mm ( Figs 80GH View FIGURE 80 ) .

Type locality. Borelli ( Piedmont, Italy) .

Type stage. Miocene (Tortonian).

Etymology. The name honors Michael J. Vendrasco (Pasadena City College, U.S.A.), for his prominent contribution to the study of Recent and fossil chitons.

Material examined. Miocene (Tortonian): Italy: Borelli: type material. Maximum width of the valves: 4.3 / -- / 4 mm .

Diagnosis. Head valve semicircular, tail valve semicircular, mucro not very prominent in anterior position, AMA short. Tegmentum granulose, sculptured with radial irregular striae of roundish granules in HV, PMA, and with longitudinal irregular granulose ribs in AMA.Articulamentum with apophyses short and wide, insertion lamina with 7 slits in holotype.

Description. Intermediate valves unknown. Head valve semicircular, posterior margin widely V-shaped, with a rounded notch at apex. Tail valve semicircular, width more twice length (W/L = 2.13), anterior margin straight, more elevated and slightly concave between apophyses, mucro not very prominent in anterior position, AMA short, antemucronal and postmucronal slopes almost straight.

Tegmentum granulose. HV and PMA sculptured with radial irregular striae of roundish granules (ca. 40 in PMA), obsolete towards apex or mucro, with evidence of irregularly arranged granules. AMA sculptured with longitudinal irregular granulose ribs, also in JA.

Articulamentum with apophyses short and wide, insertion lamina divided into short and rough denticles of irregular width, 7 slits in holotype.

Remarks. The fossil record of Stenosemus vendrascoi sp. nov. is limited to the Mediterranean upper Miocene of Italy. Only one head and two tail valves are present in the material examined. Also for this species the attribution to the genus Stenosemus is tentative, and the same considerations already expressed for Stenosemus juliuspisai sp. nov. apply (see above).

The shape of the tail valve designed as paratype shows some difference in the antemucronal (slightly convex) and postmucronal (slightly concave just under mucro), but the other characters (tegmentum sculpture, W/L, AMA short) agree, and we consider these variations to be part of intraspecific variability.

Comparisons. See Tab. 12 for a comparison with the Stenosemus spp . considered in the present study.

Distribution. Upper Miocene: Proto-Mediterranean Sea (Tortonian): Po Basin, N. Italy: Borelli (this study).

Genus Connexochiton Kaas, 1979

= Bathychiton Dell’Angelo & Palazzi, 1988

Type species. Connexochiton platynomenus Kaas, 1979 View in CoL , by original designation.

Distribution. Connexochiton is known from Pleistocene to Recent, with six living species known from the Atlantic, Indian and Pacific Oceans, and the Mediterranean Sea ( Sirenko 2021a). The fossil record includes the lower Miocene of France ( Dell’Angelo et al. 2018a) and the Pliocene-Pleistocene of Italy ( Dell’Angelo & Palazzi 1988, 1994; Dell’Angelo et al. 2013).

Remarks. The genus Connexochiton Kaas, 1979 has been recently revised by Sirenko (2021a). The main morphological characters of the Connexochiton spp . considered in the present study are reported in Tab. 11, together with the species of the genus Stenoplax .